The invention relates to container apparatuses and methods for steeping tea, especially green tea, in generally anaerobic conditions. Tea steeped in the ways and means described in conjunction with this invention can be rich in antioxidants.
Aqueous extract of the dried leaves of tea trees, Camellia sinensis, which is generally referred to as tea, has been used as a favorite beverage in certain societies for about 5,000 years for its soothing taste and for its potential health benefits to human beings. Only in the past few decades has scientific data clearly demonstrated a positive relationship between regular tea drinking and the prevention of certain human diseases. Recently numerous medical and scientific reports have indicated that tea drinking may be associated with a wide range of health benefits, including lowering the total blood cholesterol and the low-density-lipid cholesterol level, increasing the high-density-lipid blood cholesterol level, reducing blood pressure, acting as blood thinner, reducing the risk of heart attack, decreasing the risk of stroke, reducing the risk of cancer, enhancing the immune system of the body and preventing dental cavities.
Results from studies in rats, mice and hamsters showed that tea consumption protects against lung, forestomach, esophasus, duodenum, pancreas, liver, breast, colon, and skin cancers induced by chemical carcinogens. Regular consumption of green tea has a preventive effect against atherosclerosis, hypercholesterolemia, and hypertension (Hasan Mukhtar and Hihal Ahmad, Am J Nutr 71:1698S-1702S, 2000). The growth of certain types of high-grade human non-Hodgkin""s lymphoma cells can be inhibited by green tea extracts in animal models. Green tea extracts were found to be more effective than the chemotherapeutic drug cyclophosphamide in preventing lymphoma recurrence (Bertolini F et al. Leukemia 14: 1477-1482, 2000). Tea extracts also appear to have antiviral effects by interference with virus adsorption to target cells (Nakayama M et al. Letters in Applied Microbiology 11:38-40, 1990; Mykoyama A et al. Japan J Med Sci Biol.44: 181-186, 1991).
The published research data indicated that the health-promoting active ingredients in the tea leaves belong to a family of chemicals, functionally referred to as xe2x80x9cantioxidantsxe2x80x9d which also exist in many plant foods loosely labeled as xe2x80x9cflavonoidsxe2x80x9d. Most researchers have identified the health-beneficial antioxidants in tea leaves to be polyphenols, known in chemical terms as (xe2x88x92) epigallocatechin gallate (EGCG), (xe2x88x92) epigallocatechin (EGC), (xe2x88x92) epicatechin gallate (ECG), and (xe2x88x92) epicatechin (EC) (referred hereafter generally as catechins). These active polyphenolic compounds may account for 30-40% of the extractable solids of green tea leaves (Brown Md., Altem Med Rev. 4:360-370, 1999) although it is possible that other important ingredients of tea beneficial to human health are as yet to be identified (Ohe T. et al. Mutat. Res. 496:75-81, 2001).
One of the most important discoveries in medical research of recent years is the finding of the toxic effects of the so-called free radicals in human body. Free radicals, which are often reactive oxygen species, are highly reactive molecules that can damage the cells of the human body and contribute to many diseases and to the aging process. A free radical takes an electron from another molecule, turning the latter molecule into an electron-deficient free radical that will rob an electron from yet another molecule. In such a chain reaction, some of normal cellular structures reacting with the free radicals may be damaged. These damages may be apparent immediately or may be latent.
The harmful effects of free radicals on the human cells include causing oxidation of the fats and proteins of the cell membranes, damaging the mitochondria, interference with normal cellular functions by inactivating enzymes and hormones and damaging the DNA code leading to irreversible mutation and development of cancer.
Free radicals are being created constantly in the human body as part of the normal living process, or can be introduced from the environment in the form of nitrogen dioxide and other potentially harmful chemicals in the air pollutants, toxic wastes and pesticides. Ultraviolet radiation from the sun, cigarette smoking (active or passive), various medications, etc. all introduce free radicals into the human body. Therefore, there is no way to avoid free radicals completely in life. However, some nutrient supplements are known to help the body to minimize the harmful effects of free radicals. For example, the flavonoids can prevent the formation of free radicals, and protect vitamin C which can neutralize free radicals in the extracellular and intracellular fluids. Vitamin E can protect the cell membranes from the oxidation damage induced by free radicals. The carotenoids can scavenge singlet oxygen molecules and prevent the oxidation of fats which are essential components of cell membranes.
The tea polyphenols as antioxidants in the flavonoid family are capable of preventing the formation of free radicals or interrupting the chain reaction of free radical formation by donating their loosely attached electrons to the free radicals, making the latter inactive and harmless without becoming free radicals themselves. Therefore, tea polyphenols are ready electron donors and their antioxidant function must be maintained or preserved in the dried tea leaves and in the tea extracts for the latter to be effective as a health-promoting herbal beverage.
Exposure to oxygen may reduce the contents of tea polyphenols. For example, the process of fermentation which is actually an oxidation treatment of the tea leaves for 60 to 120 minutes in preparing black tea has been shown to cause more than 80% degradation of the tea catechins in the tea leaves with no decrease in caffeine contents (Astill C et al. J. Agric. Food Chem. 49:5340-5347, 2001). Therefore, most medical and scientific data have been based on studies using the unfermented green tea extracts as the active substance.
The antioxidant activities of tea catechins, especially EGCG, the most abundant and most active catechin in tea extracts, are influenced by the pH and metal ions in the aqueous extracts remaining high and constant at pH 6-12, but decreasing in acidic and strong alkaline solutions. While copper ions increase the antioxidant activity of EGCG, ferrous ions inhibit the activity (Kumamoto M et al. Biosci. Biotechnol. Biochem. 65:126-132, 2001).
The EGCG contents in the dried tea leaves vary greatly not only with the types of dried tea leaves processed with different methods, but are also known to vary between leaves plucked from different parts of the same tea tree. The first young leaf has been shown to have the highest concentration of EGCG, and the concentration of EGCG decreases with aging of the leaf (Sakata I et al. Yakugaku Zasshi 111:790-793, 1991).
Khokhar and Magnusdottir (Khokhar S. and Magnusdottir S. G. M. J. Agric. Food Chem. 50:565-570, 2002) studied the efficiency of aqueous extraction of tea catechins from dried tea leaves. The results showed that a high temperature of 100xc2x0 C. for 5 minutes is necessary for the most efficient extraction of tea catechins. At a lower temperature, for example, at 80xc2x0 C., the extraction efficiency for EGCG is reduced by more than one third (⅓).
Degradation of the green tea catechins in tea drinks has also been studied (Chen Z. et al. J. Agric. Food Chem. 49:477-482, 2001). The results showed that the green tea catechins, namely (xe2x88x92) epigallocatechin gallate (EGCG), (xe2x88x92) epigallocatechin (EGC), (xe2x88x92) epicatechin gallate (ECG) and (xe2x88x92) epicatechin (EC) are generally stable at room temperature. However, at high temperature in the presence of oxygen, especially during autoclaving at 120xc2x0 C. with addition of sucrose, citric acid, and ascorbic acid, unpredictable degradation of the tea catechins will take place. As a result, a person will ingest 400-500 mg of green tea catechins if one cup of tea drink is properly brewed in the xe2x80x9ctraditional mannerxe2x80x9d. In contrast, a person will ingest only 3-60 mg of green tea catechins when one canned or bottled tea drink of 250 ml is consumed. Oxidation and epimerization of EGCG to (xe2x88x92) gallocatechin gallate during the heating process required for sterilization appear to be the mechanisms of green tea catechin degradation in the preparation of canned or bottled tea drinks. (Epimers are stereoisomers of a sugar or sugar derivative that differ in the arrangement of the hydrogen atom and the hydroxyl group on the last asymmetric carbon of a chain. The process of going from one epimer to another is called epimerization. Epimerization can occur as the result of a physical treatment, like heating, or an enzymatic activity.) In aqueous solutions, EGCG has been shown to be stable at 4xc2x0 C. for 24 hours at pH 3-9. However, it degraded to a level below 80% of the initial concentration in 24 hours at 50xc2x0 C. and pH 5. This process of degradation was further accelerated when the pH was above 5 (Proniuk S. J. Pharmaceutical Sciences 91:111-116, 2002). At pH 9 and 50xc2x0 C., all active catechins in the tea extracts had practically vanished in 24 hours, due to accelerated oxidation in the alkaline solution.
One report has suggested that the dose of polyphenols needed for effective health protection is at least 300 to 400 mg of polyphenols per day, usually taken in the form of a green tea extract that may be standardized up to 97% polyphenols, with up to 67% being EGCG (Mitscher, L. A. and Dolby, V., The Green Tea Book, Avery Publishing Group, 1998, p.141). This amount of tea catechins is usually present in one cup of tea drink if the latter is properly brewed in the xe2x80x9ctraditional mannerxe2x80x9d, using high quality dried tea leaves. However, a daily consumption of three to ten (3-10) cups a day is necessary to achieve the maximum health benefits of tea drinking. It has been reported that cancer onset in patients who had consumed over 10 cups of green tea per day was 8.7 years later among females and 3.0 years later among males, compared with patients who had consumed under three cups per day (Fujiki, H. et al. Mutat. Res. 402:307-310, 1998). Patients with stage I and II breast cancer who consumed over five cups of green tea per day experienced a lower recurrence rate and longer disease-free period than those consuming less than four cups per day (Fujiki, H. et al. J. Cancer Res. Clin. Oncol. 125:589-597, 1999). These two series of clinical studies clearly indicate a dose-effect relationship between tea drinking and cancer prevention in humans.
The daily effective volume of this health-promoting herbal beverage to be consumed depends on the levels of polyphenols, namely the active tea catechins, in the final tea extract, which in turn vary as result of many factors, including where the tea plant was grown, the age of the tea leaves when plucked, how the tea leaves were processed, how the dried tea leaves were stored and how the tea extract was brewed. Even the traditional methods of tea brewing differ from location to location in countries with a long history of tea-drinking culture. Therefore, in order to maximize the benefits of drinking tea as a herbal beverage for health-promoting purpose, it is best to select young leaves from the tea trees grown in a reputable plantation (for example, to use organically grown tea and otherwise avoid the use of insecticides), to choose a drying process with the maximum preservation of the tea catechins, to store the dried tea leaves properly to avoid oxidation, and to brew the aqueous tea extracts under conditions with minimal catechin degradation for maximum preservation of its antioxidant activities. Since oxidation is the major mechanism of tea catechin degradation, the contents of molecular oxygen in a hot tea extract should be reduced to a minimal level during tea brewing.
The traditional methods of brewing tea involve significant exposure of the tea to atmospheric oxygen, and consequently do not avoid oxidation of the xe2x80x9cantioxidantsxe2x80x9d during tea extraction. For example, one of the large tea companies in China, FML Tea Trading Co.,Ltd. has published on the Internet (Url:http://www.fmltea.com Address:Hongseng Building 21F1,Xiamen,China) the instructions to prepare tea as follows:
xe2x80x9cAdd xc2xe teaspoon of dry tea to a clear tea glass or a porcelain cup. Bring fresh, cold water to a boil, keeping it boiling for about 5 seconds. Allow the temperature to fall to approximately 185 degrees (check with a thermometer, if possible; otherwise, wait about five minutes) and fill the cup with hot water. Steep for 2-3 minutes. Sip slowly and enjoy. When the tea water goes down to one-third of the glass or cup, add hot water again for a delicious second infusion. Or, prepare by the potful . . . the tea leaves may be steeped several times (at least three), depending on the quality grade of the tea. Take time to enjoy this delicious China green tea.xe2x80x9d
Another tea company, Xianju Green Tea published The Art of Brewing and Drinking Green Tea on the web site www.worldconsortium.com/brewing with following instructions for tea brewing:
1) Ceramic Cup
Simply put 3 grams (approximately one teaspoon) of loose Green Tea into a ceramic cup (6 ounces to 8 ounces) or inside the ceramic filter of the cup if there is one. Then pour freshly boiling water (for best results please use water at the temperature of 80 degrees Celsius or 170 degree Fahrenheit) into your ceramic cup. Put a cover on top of the cup, and let it sit for 3 minutes. When one third of the tea is all that is left in the cup, you can add more hot water. You can repeat the above procedure with the same loose Green Tea leaves up to three times or more.
(2) Ceramic Tea Pot
Preheat your teapot by rinsing it with hot water. Then add the loose tea leaves according to the size of your teapot (for example, 2 teaspoons for 6 teacups of boiling water). Next, pour the freshly boiling, distilled water (80 degrees Celsius or 170 degrees Fahrenheit) into your ceramic teapot. Cover the teapot for five minutes. You may repeat the process twice using the same tea leaves.
(3) Coffee maker
Treat the loose Green Tea as if it were ground coffee by putting it in a filter paper. Proper proportion is 1 teaspoon of tea leaves for three teacups of spring water. Follow the same procedure as you would if you were brewing coffee. Water boiled through the coffee maker has the same temperature required for brewing the Green Tea. You may repeat the same process twice.
(4) Iced Green Tea
You should never brew Green Tea with hot water and then cool it to prepare cold, or iced tea. Instead, please double the amount of the Green Tea leaves used to brew it in cold water in a sealed container. This way you keep the aroma, the natural color and the medicinal health benefits of the Green Tea. The reason this way is better, is that you avoid oxidation that can occur if the tea is left open to the air in an attempt to cool it after hot brewing. The brewing time is actually very short. For example, 10-15 cups of tea can be brewed in ajar in the ice box in just 30-45 minutes.
Mitscher, L. A. and Dolby, V.(The Green Tea Book, Avery Publishing Group, 1998, p.146-147) have summarized the present art of brewing tea in four illustrations:
1. Perforated stainless steel tea ball: Simply open the ball, put in a spoonful of tea, drop the ball into a cup of freshly boiled water, pop a lid on the cup, and let the tea steep.
2. Tea Mug: These are special tea mugs that may be fitted with a perforated infuser and have their own lids.
3. Perforated stainless steel spoon to hold the tea leaves in the hot water in a cup which cannot be covered by a lid properly.
4. Tea pot which may be equipped with an infuser. This is the time-tested method of brewing tea in a pot. The tea extract is poured into serving cups when ready.
Over the years, various versions of tea brewing devices have been patented (U.S. Pat. Des. 313,144; Des. 388,274; U.S. D 444,337; U.S. D 450,522; U.S. D 448,235S; U.S. Pat. Nos. 4,526,796; 5,453,189; 5,478,586; 5,687,637; 6,152,018 and 6,324,967 B1). These are all variations of the traditional tea pot, tea cup or tea mug described above without a provision to prevent degradation and oxidation of the tea catechins during tea brewing because in these containers the tea leaves are steeped in a hot aqueous solution in contact with molecular oxygen of the free air or with molecular oxygen in a pocket of free air.
The present invention introduces a container apparatus (such as a tea steeper) and methods for using same which entail immersion and extraction of tea leaves in a hot aqueous solution not in significant contact with molecular oxygen of the free air or with molecular oxygen in a pocket of free air for the maximum preservation of the active antioxidants in the tea extracts. The containers and methods of this invention are useful to prepare tea extracts as an herbal beverage for health-promoting purpose.
In particular, with this invention dried tea leaves are steeped in hot water while the aqueous solution is not in contact with molecular oxygen of the free air or with molecular oxygen in a pocket of free air. Under these anaerobic conditions, the tea catechins extracted, for instance (xe2x88x92) epigallocatechin gallate (EGCG), (xe2x88x92) epigallocatechin (EGC), (xe2x88x92) epicatechin gallate (ECG) and (xe2x88x92) epicatechin (EC), which are functionally strong antioxidants and ready donors of electrons to neutralize the toxic free radicals in the human body, will be optimally preserved during the brewing process.
For instance, in a first embodiment, the invention entails a container apparatus for steeping intact or fragments of dried tea leaves in water, comprising a container or chamber that has (a) closable opening (such as, for instance, a valve) and that is made of inert materials that can withstand contact with water having a temperature of at least 100xc2x0 C. without releasing components or odors of the materials into the water. The container portion is formed in such a way that when the tea leaves and water are placed therein there is no significant contact between the water and atmospheric air and there is no significant amount of air trapped within the container in contact with the water. This embodiment may be useful for commercial tea brewing, and may include inlets for water and tea leaves, and outlets for air and the tea extract when it is finished brewing.
In another form, the container apparatus can comprise:
(a) a container which is made of inert materials that can withstand contact with water having a temperature of at least 100xc2x0 C. without releasing components or odors of the materials into the water, and which has a top-opening for receiving a quantity of water, and
(b) a lid sized to fit releasably on the top-opening of the container, which is made of inert materials that can withstand contact with water having a temperature of at least 100xc2x0 C. without releasing components or odors of the materials into the water. When intact or fragments of dried tea leaves and water are placed into the container and the lid is placed on the top-opening of the container, the lid is adapted such that there is no significant contact between the water and atmospheric air and there is no significant amount of air trapped under the lid in contact with the water.
In a further embodiment, the invention contemplates methods of brewing intact or fragments of dried tea leaves under generally anaerobic conditions. Such methods minimally comprise the steps of:
(a) placing a quantity of intact or fragments of dried tea leaves into a container apparatus which comprises a container or chamber that includes a closable opening and that is made of inert materials that can withstand contact with water having a temperature of at least 100xc2x0 C. without releasing components or odors of the materials into the water. The container is formed in such a way that when the tea leaves and water are placed therein there is no significant contact between the water and atmospheric air and there is no significant amount of air trapped within the container in contact with the water. That is, the container does not permit contact between the aqueous solution and the open-air, and no significant air pockets are trapped inside the container that come into contact with the aqueous solution.
(b) filling the container with water having a temperature of between about 70xc2x0 C.-100xc2x0 C.;
(c) allowing the tea leaves to be extracted in the water for at least about 10 minutes; and
(d) optionally, pouring the liquid of step (c) onto ice and storing in an air-tight container in temperatures below about 37xc2x0 C. for consumption within about 24 hours.
In a similar method, the steps include:
(a) placing a quantity of intact or fragments of dried tea leaves into a container apparatus that comprises
a container which is made of inert materials that can withstand contact with water having a temperature of at least 100xc2x0 C. without releasing components or odors of the materials into the water, and which has a top opening for receiving a quantity of water, and
a lid sized to fit releasably on the top-opening of the container, which is made of inert materials that can withstand contact with water having a temperature of at least 100xc2x0 C. without releasing components or odors of the materials into the water;
(b) filling the container with water having a temperature of between about 70xc2x0 C.-100xc2x0 C. so that the water level is at least at or near the top-opening (or even overflowing the top-opening) or up to a pre-marked position on the container;
(c) immediately placing the lid onto the top-opening of the container so that there is no significant contact between the water and atmospheric air and there is no significant amount of air trapped under the lid in contact with the water;
(d) allowing the tea leaves to be extracted in the water for at least about 10 minutes or until the water temperature cools to a safely drinkable temperature; and
(e) optionally, pouring the liquid of step (d) onto ice and storing in an air-tight container in temperatures below about 37xc2x0 C. for consumption within about 24 hours.
The conditions for these containers and methods of use are described as generally anaerobic. By this it is meant that the hot aqueous solution in the tea steeper is largely devoid of oxidizing gases, such as molecular oxygen and chlorine, which have been driven out of the water used to brewing the tea by boiling, and is prevented from reabsorbing molecular oxygen from the air during tea steeping. It is understood that the conditions of brewing and steeping the tea are not absolutely air-free, since most of the embodiments of the container apparatus will not have top openings that are hermetically sealed when brewing takes place (although hermetically sealed containers are contemplated as desired). While it is preferred that steeping of the tea take place in the complete absence of oxygen, it is understood that in practice this may be inconvenient or otherwise difficult to achieve for most users, and as demonstrated below in the examples the complete 100% absence of all oxygen during brewing is not essential to prepare a tea that is rich with antioxidants.